<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    const  filename = "aa.xls";
    var strings = filename.split(".");
    console.log(strings)

    var suffix = strings[strings.length - 1];
    console.log(suffix);




</script>
</body>
</html>